A conventional projection screen is apt to melt at high temperature because the image area of the screen is made up of inflammable material such as polyvinyl chloride (PVC), plastic, etc. In addition, the conventional screen can not be employed in closed spaces used by many people such as subways, department stores, etc. This is because in case of fire the screen melts in the closed space, thereby generating a poisonous gas which might cause the death of many people.
In a spherical screen using an aluminum thin film disclosed in Korean Patent No. 100127, the aluminum thin film should have ductility in order to form a screen into a spherical shape. As a result, the strength of the surface of the screen is decreased and the surface of the screen might be damaged during removing foreign material thereon. This durability of the aluminum thin film may be complemented by coating the surface of the aluminum thin film with material of high durability. However, the coating increases the durability of the aluminum thin film only within the limited ranges. In addition, the image sharpness of the screen is decreased because the coated film deteriorates the light transmittance, and also the spherical screen should not be used outdoors having a lot of dust. Furthermore, the screen is ignitable in case of fire because the spherical screen is composed of about 5% of aluminum thin film and about 95% of the plastic. Here, the aluminum thin film employed in the spherical screen has the thickness of less than 50 micron.
A known conventional film screen includes one side which is a scattering surface and the other side which is a reflection surface. In this case, an interference phenomenon is noticeably generated on the scattering surface of the screen so that the image sharpness of the film screen is decreased. In addition, because the major material of the film screen is plastic, it is not easy to clean the screen and in case of fire the film screen is ignitable.
Most of known conventional transmission type screens relate to transmission and scattering type screen including light-diffusion elements consisted of plastic material. In other words, the conventional screens limit the material thereof to plastic because of characteristics of use and manufacture. Hence, in case of fire the projection screens are ignitable.
As described above, in case of fire most of the conventional screens act as inflammables and toxic material. Additionally, it is not easy to remove foreign material, such as dust and others, on the surface of the screen, so the screen may not be suitable to indoors as well as outdoors in view of safety and maintenance.